With continuous printing presses and similar machines where the web material fed out has to be wound up on roll spindles, a plurality of systems have been developed for shifting the roll spindles without interrupting the feed of the web material. As a rule these known systems include some form of web material buffer store in the form of an extra loop which can be enlarged in conjunction with a transient reduction in the winding-up speed when the material web is to be cut off so as to enable the roll to be shifted. Generally the known methods and apparatuses of this type have the disadvantage that the acceleration and retardations in conjunction with winding-up, and particularly during the initial stage of winding-up, result in uncontrolled stretching of the material web which in turn results in uneven winding-up, problems of registration and the like in the preceeding rotary printing press.
It is also conventional to have some form of metrological coupling or drive from the rotary printing press or the like which is served by the winding-up unit. However experience has indicated that these couplings can easily give rise to oscillations in the control system. This causes variations in web tension which in turn result in winding-up becoming uneven. In many cases the stretch of the web material is not optimum. One consequence of these problems is that with conventional arrangements there are often gaps between the turns on the roll, which naturally renders this less compact and more uneven. In such cases the rolls can easily become distorted and be difficult to handle. A disadvantage of existing systems is also that generally it is difficult to reproduce the good winding-up results obtained in favourable cases. This applies particularly, if the winding-up unit is to be employed with a variety of web material grades.